Determination of transfer factors for 137Cs and 90Sr isotopes in soil–plant system

Studies on the determination of transfer factors (TF) for ¹³⁷Cs and ⁹⁰Sr isotopes from soil to plant are presented. Experiments were performed on grass from meadows of Bug river valleys and vegetables from Zwierzyniec region. The influence of potassium and calcium on the transfer factor of both isotopes is discussed.     

Cs–Ba separation using N2O as a reactant gas in a Multiple Collector-Inductively Coupled Plasma Mass Spectrometer collision-reaction cell: Application to the measurements of Cs isotopes in spent nuclear fuel samples

In the general frameworks of the nuclear fuel cycle and environmental research field, the Cs isotopic composition must be known with high precision and accuracy. The direct determination of Cs isotopes by mass spectrometry techniques is generally hampered by the presence of Ba isobaric interferences however. Here we present a new method which takes advantage of the collision-reaction cell based Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and allows to analyse Cs isotopes in the presence of Ba without prior separation step. The addition of N₂O gas in the cell leads to an antagonistic behavior of Cs⁺ and Ba⁺ as the latter reacts with the gas to form BaO⁺ and BaOH⁺ products whereas Cs⁺ remains unreactive. The efficiency of the method was demonstrated for an UOx sample by comparing the results obtained (1) from the measurements of pure Cs fractions and (2) from Fission Products fractions containing more than 30 ionisable elements in addition to Cs, Ba, and where U and Pu were previously removed by using ion exchange resin. An excellent agreement is achieved between each set of experiments with an external reproducibility always better than 0.5% (RSD, k = 2). This study confirms the strong potential of collision–reaction cell to measure Cs isotopes in presence of interfering Ba, precluding therefore former systematic chemical separations.     

Photodegradation of methylene blue in water,a standard method to determine the activity of photocatalytic coatings?

The degradation of methylene blue (MB) in aqueous solutions has been re-examined as a method to characterize the photocatalytic activity of transparent TiO₂ coatings. Increasing irradiation intensities leads to a change in the observed kinetic behavior from zero-order to pseudo-first-order regarding the concentration of MB. This is due to a diffusion inhibition of MB. In order to obtain data within a zero-order kinetic regime at an initial MB concentration of 10 μmol/l and, thus, to avoid the diffusion control, irradiation intensities below E=5 W/m² for substrates comprising higher photonic efficiencies than ζ=0.09% have to be applied. Recommendations for a standard protocol are given.     

Allosteric effects in norbadione A. A clue for the accumulation process of 137Cs in mushrooms?

A fruitful combination of potentiometry, absorption spectrophotometry, ESMS and 1H NMR enabled the characterisation of two caesium complexes with norbadione A and the determination of the respective stability constants of a mononuclear and a dinuclear caesium complex at pH approximately 6; a preliminary study allowed the assignment of five protonation sites of this pigment; a positively cooperative binding of the second Cs+ cation was observed.     

Neural networks for prediction of ultrafiltration transmembrane pressure – application to drinking water production

Modelling of ultrafiltration plants for drinking water production appears as a necessary step before plants control and supervisory. It first requires a better knowledge about membrane fouling by natural waters. The phenomena involved are very complex, because of the nature of the fluid concerned: water. Thus up to now phenomenological model cannot be applied for resource waters. Because of their properties, new modelling tools called neural networks seem to be a promising way to model complex phenomena and therefore to be applied to water treatment. In the present study a neural network is used to model the time evolution of transmembrane pressures for ultrafiltration membranes applied to drinking water production. Different network structures and architectures have been elaborated and evaluated with the aim of computing the pressure at the end of a filtration cycle and after the next backwash. For some of these networks a very good accuracy is obtained for both pressures predictions. The inlets are permeate flow rate, turbidity during the cycle and pressure measurements at the cycle start and at the end of the previous cycle. These networks are able to model the effect of both reversible and irreversible fouling on pressures even if no inlet parameter concerning organic matters is considered.     

Monitoring three typical phenol endocrine disrupting compounds in drinking water of Suzhou urban area – from raw water to tap water

In this work, three typical phenol endocrine-disrupting compounds (EDCs), namely Bisphenol A (BPA), 4-nonylphenol (4-NP) and 4-tert-octyphenol (4-t-OP), were detected in water samples from the whole drinking water supply chain of seven water plants at three hydrographic periods in Suzhou, China. Almost all of the drinking water in urban area of Suzhou city is provided by the seven water plants. Every link of drinking water supply, including raw water, finished water and tap water were monitored. The results indicated that BPA and 4-NP were detected in all samples with the concentration of 0.067–0.118 μg L^?1 and 0.111–0.350 μg L^?1, respectively, while 4-t-OP could be detected in only a few raw water samples with the concentration lower than its limit of quantitation (LOQ). The levels of BPA and 4-NP in raw water were significantly different among three hydrographic periods and the highest concentration can be observed in dry period. The difference in removal efficiency of BPA and 4-NP in seven water plants was also observed among three hydrographic periods, e.g. relative higher in dry period for BPA and in flow period for 4-NP. Potential risk assessment hinted that BPA and 4-NP in raw water showed a low to medium and a medium to high risk respectively to aquatic environment, while in tap water, the health risk from BPA and 4-NP could be ignored on human.     

Application of β-cyclodextrin in polymeric solid phase for separation and determination of lead in different environmental matrices

Immobilization of β-cyclodextrin on Dowex resin as an insoluble polymeric matrix by covalent bond presents a new solid-phase medium for preconcentration of Pb (II) at trace level in environmental samples prior to its flame atomic absorption spectrometric determination. The method is based on the sorption of lead after passing on modified Dowex sorbent in a column. The effect of several parameters such as pH, flow rate of sample, eluent kind and volume was investigated. The sorption capacity of the matrix has been found to be 0.4996?mg?g^?1 of adsorbent with the preconcentration factor of 250 for Pb (II). Nitric acid (3 M) as an eluent was sufficient to obtain quantitative recovery (>95%) for Pb (II). The optimum flow rate was 10?ml?min ^?1. The calibration curve was linear in the range of (3–250?ng?mL^?1) with a correlation coefficient of 0.9995. The limit of detection (LOD) based on three times the standard deviation of the blank was 1.37?ng?mL^?1. The relative standard deviation (RSD) for determination of 10?ng?mL^?1 and 100?ngmL^?1 of Pb (II) was 3.00 % and 0.58 % (n?=?10), respectively. The method was successfully applied to determination of lead in some environmental samples such as tap water, river water, soil and rice.     

Ionic liquid-based dispersive liquid–liquid microextraction for the separation and preconcentration of lead in water samples prior to FAAS determination without chelating agent

In the present study, an environment-friendly sample preparation method termed ionic liquid-based dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometry has been developed for the determination of Pb(II) ion in water samples prior to flame atomic absorption spectrometry determination. In this method, ionic liquid was used as an extraction solvent instead of the organic solvent used in the conventional dispersive liquid–liquid microextraction (DLLME) assay, and there is no need for a chelating agent. Several variables that may affect extraction efficiencies, including pH, the volume of ionic liquid, the type and volume of disperser solvent, salt addition, and the time for centrifugation and extraction were studied and optimised. Under the optimised conditions, the calibration curve exhibited linearity over the range of 20.0–1000.0 μg L^?1. The enrichment factor and the limit of detection based on 3S_b/m were 35.0 and 5.9 μg L^?1, respectively. Seven replicate determination of a solution containing of 100.0 μg L^?1 Pb(II) ions gave a relative standard deviation of ±2.1%. Finally, the feasibility of the proposed method for Pb(II) determination was assessed by the analysis of certi?ed reference material and various water samples and the satisfactory results were obtained.     

Application of Pac Ester in Thioester Method for the Synthesis of Cyclopentapeptides

Thioester method for the synthesis of cyclopeptides is improved by using Pac (Pac = phenacyl, CH2COC6Hs) ester as a protecting group of 3-mercaptopropionic acid. The Pac group is easy to be removed from C-terminal with zinc in acetic acid. The protected glycine thioester and peptide thioesters synthesized by the improved method, are easy to be purified, so the final linear peptides are pure enough for the following cyclization. Furthermore, this method is flexible for peptide chain elongation,either from C-termlnal or from N.terminal. So it is an efficient and practical method for synthesis of bioactive peptides. Two N-protected pentapeptide thioesters, Boc-Pro-Tyr-Leu-Ala-GIySCH2CH2COOPac and Boc-Ala-Tyr-Leu-Ala-Gly-SCH2CH2COOPac were synthesized by the improved thloester method.After deprotecting Pac ester with zinc in aqueous acetic acid and Boc group with trifluoroacetic acid in CH2C12, two free pentapeptide tldoesters were obtained. Ag^ -assisted cyclization in acetate buffered solution afforded two cyclic pentapeptides c(Pro-Tyr-Leu-Ala-Gly) and c(Ala-Tyr-Leu-Ala-Gly).Effects of different buffer pH, different Ag^ concentrations, etc. on the cyclization were studied.     

Development of a method for the estimation of low amount of plutonium in 200 L waste drums in presence of high amount of β γ activity due to 137Cs and 60Co

The waste drum monitoring system based on HPGe detector was used to study its performance for the estimation of low amounts of plutonium in presence of high activity of ¹³⁷Cs and ⁶⁰Co. The counting was carried out by keeping amount of plutonium constant at 100 mg level and varying the count rate for the γ rays of ¹³⁷Cs and ⁶⁰Co. Present study has shown that the estimation of low amount of ²³⁹Pu in a waste drum can be carried out using 129 keV γ ray in the presence of ¹³⁷Cs up to an activity level of 16 mCi and in the presence of ⁶⁰Co up to an activity level of 8 mCi.     

Chitosan/N-methylol nylon 6 blend membranes for the pervaporation separation of ethanol–water mixtures

Blend membranes of chitosan and N-methylol nylon 6 were prepared by solution blending. Their pervaporation performances for the separation of ethanol–water mixtures were investigated in terms of acid (H₂SO₄) post-treatment, feed concentration, blend ratio and temperature. The pervaporation performance of the blend membranes was significantly improved by ionizing with H₂SO₄. The blend ratio of chitosan and N-methylol nylon 6 plays a different role at feed solutions of low and high water content. At a feed solution having low water content, an increase in chitosan content caused a decrease in permeability and an increase in separation factor. At a feed solution having high water content, the permeability increases with an increase in chitosan content, while the separation factor shows a maximum value around 60 wt% chitosan. It is proposed that extra permeation channels generated from the phase separation boundary between ionized chitosan and N-methylol nylon 6 account for the abnormal temperature dependence of pervaporation performance of the blend membranes.     

Development and validation of a liquid chromatography tandem mass spectrometry method for the analysis of β-agonists in animal feed and drinking water

A reproducible, sensitive and selective multiresidue analytical method for seven β-agonists: clenbuterol (CBT), clenpenterol (CPT), ractopamine (RTP), brombuterol (BBT), mabuterol (MBT), mapenterol (MPT), and hydroxymethylclenbuterol (HMCBT) was developed and validated by using liquid chromatography tandem mass spectrometry (LC–MS/MS) in feed and drinking water samples. The validation was achieved according to the criteria laid down in the Commission Decision 2002/657/EC, however it was necessary to use minimum required performance limits (MRPLs) proposed by the Community Reference Laboratories (CRLs) due to the lack of maximum residue limits (MRLs) for β-agonists. By setting up these MRPLs, allows controlling their use in safe mode, since β-agonists are commonly used in veterinary medicine sometime in a fraudulent manner, for increasing the weigh of animals. Values set for both matrices studied are 50 μg/kg for animal feed, and a range from 0.2 to 10 μg/L for drinking water. CCα values calculated were under the MRPLs suggested; for drinking water the lowest value obtained was 0.12 μg/L, and for animal feed 0.87 μg/kg. Values for CCβ were ranged from 0.08 to 0.13 μg/L in drinking water and from 0.5 to 0.92 μg/kg in animal feed samples. The excellence values obtained, allowed us to conclude that the proposed analytical method is capable to control the β-agonists studied in both matrices and that it can be successfully applied and used as a routine method in laboratories of residue analysis of veterinary food control.     

Synthesis and characterization of ammonium molybdophosphate–silica nano-composite (AMP–SiO2) as a prospective sorbent for the separation of 137Cs from nuclear waste

The ammonium molybdophosphate–silica (AMP–SiO₂) nano-composites were prepared by sol–gel method. The material synthesized was nanocrystalline, with average crystallite size of primary particles in the range of 10–25 nm. Small angle X-ray scattering showed presence of mass fractal aggregates made of small particles with rough pore boundaries. To realize the scope of using AMP–SiO₂ nano-composites sorbent for removal of ¹³⁷Cs from nuclear waste solutions, its adsorption characteristics for cesium were evaluated. It was found that the AMP–SiO₂ nanocomposites were amenable for column operation, have high affinity for Cs, and possess very high adsorption capacity for Cs. From the perspective of separation of ¹³⁷Cs from acidic radioactive waste solution, AMP–SiO₂ nanocomposite holds significant promise.     

The evaluation of 137Cs radioactivities in soils taken from the Babia Góra National Park

The aim of this work was to determine ¹³⁷Cs and ⁴⁰K radioactivities in soil samples taken from the Babia Góra National Park (BPN) in south Poland. The cluster analysis (CA) and principal component analysis (PCA) were used to discuss the obtained data. 10 cm thick soil cores were collected from the BPN area. Each sample was divided into three sub-samples. The samples were dried, homogenized and packed in polyethylene containers. The radioactivities of ¹³⁷Cs and ⁴⁰K were measured by means of gamma spectrometry. It was found that ¹³⁷Cs radioactivity in the whole 10 cm soil cores was in the range from 1,916 to 28,551 Bq m^?2. The radioactivity of ⁴⁰K varied from 1,642 to 25,654 Bq m^?2. Using CA it was possible to diverse the soils taking into account soil types. By use of the PCA method, it was chosen three factors which are appropriate to characterize researched parameters.